javax.microedition.io.file
Interface FileConnection

This interface is intended to access files or directories that are located on
removeable media and/or file systems on a device.

Device internal filesystems in memory may also be accessed through
this class as well, provided there is underlying hardware and OS support.
If file connections are not supported to a particular media or file system,
attempts to open a file connection to the media or file system through
Connector.open() results in an
javax.microedition.io.IOException being thrown.

Establishing a Connection

The format of the input string used to access a FileConnection through
Connector.open() must follow the format of a fully-qualified,
absolute path file name as described by the file
URL format in IETF RFCs 1738 & 2396. Further detail for the File
URL format can be found in the javax.microedition.io.file package description.

A single connection object only references a single file or
directory at a time. In some cases, a connection object can be reused to
refer to a different file or directory than it was originally associated with
(see setFileConnection(java.lang.String)). In general, the best approach to reference
a different file or directory is by establishing a completely separate
connection through the Connector.open() method.

FileConnection Behavior

File connection is different from other Generic Connection Framework
connections in that a connection object can be successfully returned from
the Connector.open() method without actually referencing an
existing entity (in this case, a file or directory). This behavior
allows the creation of new files and directories on a file system.
For example, the following code can be used to create
a new file on a file system, where CFCard is a valid existing file
system root name for a given implementation:

try {
FileConnection fconn = (FileConnection)Connector.open("file:///CFCard/newfile.txt");
// If no exception is thrown, then the URI is valid, but the file may or may not exist.
if (!fconn.exists())
fconn.create(); // create the file if it doesn't exist
fconn.close();
}
catch (IOException ioe) {
}

Developers should always check for the file's or directory's existence
after a connection is established to determine if the file or directory
actually exists. Similarly, files or directories can be deleted using the
delete() method, and developers should close the connection
immediately after deletion to prevent exceptions from accessing a connection
to a non-existent file or directory.

A file connection's open status is unaffected by the opening and closing of
input and output streams from the file connection; the file connection stays
open until close() is invoked on the FileConnection instance.
Input and output streams may be opened and closed multiple times on a
FileConnection instance.

All FileConnection instances have one underlying
InputStream and one OutputStream. Opening a
DataInputStream counts as opening an InputStream,
and opening a DataOutputStream counts as opening an
OutputStream. A FileConnection instance can have
only one InputStream and one OutputStream open at
any one time. Trying to open more than one InputStream or more
than one OutputStream from a StreamConnection
causes an IOException. Trying to open an InputStream
or an OutputStream after the FileConnection has
been closed causes an IOException.

The inherited StreamConnection methods in a
FileConnection instance are not synchronized. The only stream
method that can be called safely from another thread is close.
When close is invoked on a stream that is executing in another
thread, any pending I/O method MUST throw an
InterruptedIOException. In the above case, implementations
SHOULD try to throw the exception in a timely manner. When all open streams
have been closed, and when the FileConnection is closed, any
pending I/O operations MUST be interrupted in a timely manner.

Data written to the output streams of these FileConnection
objects is not guaranteed to be flushed to the stream's destination
(and subsequently made available to any input streams) until either
flush() or close() is invoked on the stream.

Security

Access to file connections is restricted to prevent unauthorized manipulation
of data. The access security model applied to the file connection
is defined by the implementing profile. The security model is applied on
the invocation of the Connector.open() method with a valid file
connection string. The mode provided in the open() method
(Connector.READ_WRITE by default) indicates the application's
request for access rights for the indicated file or directory and is
therefore checked against the security scheme. All three connections modes
(READ_WRITE, WRITE, and READ) are
supported for a file connection and determine the access requested from the
security model.

The security model is also applied during use of the returned
FileConnection, specifically when the methods
openInputStream(), openDataInputStream(),
openOutputStream(), and openDataOutputStream() are
invoked. These methods have implied request for access rights (i.e.
input stream access is requesting read access, and output stream access is
requesting write access). Should the application not be granted the
appropriate read or write access to the file or file system by the profile
authorization scheme, a java.lang.SecurityException is thrown.

File access through the File Connection API may be restricted to files that
are within a public context and not deemed private or sensitive. This
restriction is intended to protect the device's and other users' files and
data from both malicious and unintentional access. RMS databases cannot be
accessed using the File Connection API. Access to files and directories that
are private to another application, files and directories that are private to
a different user than the current user, system configuration files, and
device and OS specific files and directories may be restricted. In these
situations, a java.lang.SecurityException is thrown from the
Connector.open() method if the file, file system, or directory
is not allowed to be accessed.

availableSize

public long availableSize()

Determines the free memory that is available on the file system the file
or directory resides on. This may only be an estimate and may vary based
on platform-specific file system blocking and metadata information.

Returns:

The available size in bytes on a file system, or -1 if the
file system is not accessible.

Throws:

SecurityException - if the security of the application does not
have read access to the root volume.

IllegalModeException - if the application does have read access
to the directory but has opened the connection in
Connector.WRITE mode.

canRead

public boolean canRead()

Checks if the file or directory is readable. This method checks the
attributes associated with a file or directory by the underlying file
system. Some file systems may not support associating attributes with
a file, in which case this method returns true.

Returns:

true if the connection's target exists, is accessible, and
is readable, otherwise false.

Throws:

SecurityException - if the security of the application does not
have read access for the connection's target.

IllegalModeException - if the application does have read access
to the connection's target but has opened the connection in
Connector.WRITE mode.

canWrite

public boolean canWrite()

Checks if the file or directory is writable. This method checks the
attributes associated with a file or directory by the underlying file
system. Some file systems may not support associating attributes with
a file, in which case this method returns true.

Returns:

true if the connection's target exists, is accessible, and
is writable, otherwise false.

Throws:

SecurityException - if the security of the application does not
have read access for the connection's target.

IllegalModeException - if the application does have read access
to the connection's target but has opened the connection in
Connector.WRITE mode.

create

Creates a file corresponding to the file string
provided in the Connector.open() method for this FileConnection. The
file is created immediately on the actual file system upon invocation of
this method. Files are created with zero length and data can be put into
the file through output streams opened on the file. This method does not
create any directories specified in the file's path.

Throws:

SecurityException - if the security of the application does not
have write access for the file.

IllegalModeException - if the application does have write access
to the file but has opened the connection in
Connector.READ mode.

IOException - if invoked on an existing file or on any directory
(mkdir() is used to create directories), the
connection's target has a trailing "/" to denote a
directory, the target file system is not accessible, or an
unspecified error occurs preventing creation of the file.

delete

Deletes the file or directory specified in the
Connector.open() URL. The file or directory is deleted immediately on
the actual file system upon invocation of this method. All open input
and output streams are automatically flushed and closed. Attempts to
further use those streams result in an IOException. The
FileConnection instance object remains open and available for use.

fileSize

Determines the size of a file on the file system. The size of a file
always represents the number of bytes contained in the file; there is
no pre-allocated but empty space in a file.

fileSize() always returns size of the file on the file system,
and not in any pending output stream. flush() should be used
before calling fileSize() to ensure the contents
of the output streams opened to the file get written to the file system.

Returns:

The size in bytes of the selected file, or -1 if the
file does not exist or is not accessible.

getName

Returns the name of a file or directory excluding the URL schema and
all paths. Directories are denoted with a
trailing slash "/" in their returned name. The String resulting
from this method looks as follows:

<directory>/

or

<filename.extension>

or if no file extension

<filename>

Returns:

The name of a file or directory.

Since:

JDE 4.2.0

getPath

Returns the path excluding the file or directory name and the "file" URL
schema and host from where the file or directory specified in the
Connector.open() method is opened. getName() can be appended to
this value to get a fully qualified path filename. The String resulting
from this method looks as follows:

/<root>/<directory>/

Returns:

The path of a file or directory in the format specified above.

Since:

JDE 4.2.0

getURL

Returns the full file URL including
the scheme, host, and path from where the file or directory specified
in the Connector.open() method is opened. The string returned is in
an escaped ASCII format as defined by RFC 2396.
The resulting String looks as follows:

file://<host>/<root>/<directory>/<filename.extension>

or

file://<host>/<root>/<directory>/<directoryname>/

Returns:

The URL of a file or directory in the format specified above.

Since:

JDE 4.2.0

isDirectory

public boolean isDirectory()

Checks if the URL passed to the Connector.open() is a directory.

Returns:

True if the connection's target exists, is accessible, and
is a directory, otherwise false.

Throws:

SecurityException - if the security of the application does not
have read access for the connection's target.

IllegalModeException - if the application does have read access
to the connection's target but has opened the connection in
Connector.WRITE mode.

Since:

JDE 4.2.0

isHidden

public boolean isHidden()

Checks if the file is hidden. The exact definition of hidden is
system-dependent. For example, on UNIX systems a file is considered to be
hidden if its name begins with a period character ('.'). On Win32 and
FAT file systems, a file is considered to be hidden if it has been marked
as such in the file's attributes. If hidden files are not supported on
the referenced file system, this method always returns false.

Returns:

true if the file exists, is accessible, and is hidden,
otherwise false.

isOpen

Returns an indication of whether the file connection is currently
open or not.

Returns:

true if the file connection is open, false otherwise.

Since:

JDE 4.2.0

lastModified

public long lastModified()

Returns the time that the file denoted by the URL specified
in the Connector.open() method was last modified.

Returns:

A long value representing the time the file was last
modified, measured in milliseconds since the epoch
(00:00:00 GMT, January 1, 1970), or 0L if an I/O error occurs.
If modification date is not supported by the underlying platform
and/or file system, then 0L is also returned.
If the connection's target does not exist or is not
accessible, 0L is returned.

Throws:

SecurityException - if the security of the application does not
have read access for the connection's target.

IllegalModeException - if the application does have read access
to the connection's target but has opened the connection in
Connector.WRITE mode.

list

Gets a list of all files and directories contained in a directory.
The directory is the connection's target as specified in
Connector.open().

Returns:

An Enumeration of strings, denoting the files and
directories in the directory. The string returned contain only
the file or directory name and does not contain any path prefix
(to get a complete path for each file or directory, prepend
getPath()). Directories are denoted with a
trailing slash "/" in their returned name. The Enumeration has
zero length if the directory is empty. Any
hidden files and directories in the directory are not included
in the returned list. Any current directory indication (".")
and any parent directory indication ("..") is not included
in the list of files and directories returned.

Throws:

IOException - if invoked on a file, the directory does not exist,
the directory is not accessible, or an I/O error occurs.

list

Gets a filtered list of files and directories contained in a directory.
The directory is the connection's target as specified in
Connector.open().

Parameters:

filter - String against which all files and directories are
matched for retrieval. An asterisk ("*") can be used as a
wildcard to represent 0 or more occurrences of any character.

includeHidden - boolean indicating whether files marked as hidden
should be included or not in the list of files and directories
returned.

Returns:

An Enumeration of strings, denoting the files and directories
in the directory matching the filter. Directories are denoted
with a trailing slash "/" in their returned name. The
Enumeration has zero length if the directory is empty or no
files and/or directories are found matching the given filter.
Any current directory indication (".") and any parent directory
indication ("..") is not included in the list of files and
directories returned.

Throws:

IOException - if invoked on a file, the directory does not exist,
the directory is not accessible, or an I/O error occurs.

mkdir

Creates a directory corresponding to the directory
string provided in the Connector.open() method.
The directory is created immediately on the actual
file system upon invocation of this method. Directories in the
specified path are not recursively created and must be explicitly
created before subdirectories can be created.

Throws:

SecurityException - if the security of the application does not
have write access to the directory.

IllegalModeException - if the application does have write access
to the directory but has opened the connection in
Connector.READ mode.

IOException - if invoked on an existing directory or on any file
(create() is used to create files), the target
file sytem is not accessible, or an unspecified error occurs
preventing creation of the directory.

openDataOutputStream

Open and return a data output stream for a connection. The output stream
is positioned at the start of the file. Writing data to the output stream
overwrites the contents of the files (i.e. does not insert data).
Writing data to output streams beyond the current end of file
automatically extends the file size. The connection's target must
already exist and be accessible for the output stream to be created.
openOutputStream(long) should be used to position an output
stream to a different position in the file.

Changes made to a file through an output stream may not be immediately
made to the actual file residing on the file system because
platform and implementation specific use of caching and buffering of the
data. Steam contents and file length extensions are not necessarily
visible outside of the application immediately unless
flush() is called on the stream. The returned output stream
is automatically and synchronously flushed when it is closed.

Returns:

An open output stream

Throws:

IOException - If an I/O error occurs, if the method is invoked on
a directory, the file does not yet exist, or the connection's
target is not accessible.

IllegalModeException - if the application does have write access
to the connection's target but has opened the connection in
Connector.READ mode.

SecurityException - If the application is not granted write
access to the connection's target.

openOutputStream

Open and return an output stream for a connection. The output stream
is positioned at the start of the file. Writing data to the output stream
overwrites the contents of the files (i.e. does not insert data).
Writing data to output streams beyond the current end of file
automatically extends the file size. The connection's target must
already exist and be accessible for the output stream to be created.
openOutputStream(long) should be used to position an output
stream to a different position in the file.

Changes made to a file through an output stream may not be immediately
made to the actual file residing on the file system because
platform and implementation specific use of caching and buffering of the
data. Steam contents and file length extensions are not necessarily
visible outside of the application immediately unless
flush() is called on the stream. The returned output stream
is automatically and synchronously flushed when it is closed.

Returns:

An open output stream

Throws:

IOException - If an I/O error occurs, if the method is invoked on
a directory, the file does not yet exist, or the connection's
target is not accessible.

IllegalModeException - if the application does have write access
to the connection's target but has opened the connection in
Connector.READ mode.

SecurityException - If the application is not granted write
access to the connection's target.

openOutputStream

This method opens an output stream and positions it at the indicated
byte offset in the file. Data written to the returned output stream at
that position overwrites any existing data until EOF is reached, and
then additional data is appended. The connection's target must
already exist and be accessible for the output stream to be created.

Changes made to a file through an output stream may not be immediately
made to the actual file residing on the file system because
platform and implementation specific use of caching and buffering of the
data. Steam contents and file length extensions are not necessarily
visible outside of the application immediately unless
flush() is called on the stream. The returned output
stream is automatically and synchronously flushed when it is closed.

Parameters:

byteOffset - number of bytes to skip over from the beginning of
the file when positioning the start of the OutputStream. If
the provided offset is larger than or equal to the current file
size, the OutputStream is positioned at the current end of the
file for appending.

Returns:

an open OutputStream positioned at the byte offset in the file,
or the end of the file if the offset is greater than the size
of the file.

Throws:

IOException - If an I/O error occurs, if the method is invoked
on a directory, the file does not yet exist, or the
connection's target is not accessible.

IllegalModeException - if the application does have write access
to the connection's target but has opened the connection in
Connector.READ mode.

SecurityException - if the security if the application does not
allow write access to the file.

rename

Renames the selected file or directory to a new name in the same
directory. The file or directory is renamed immediately on the actual
file system upon invocation of this method. No file or directory by the
original name exists after this method call. All previously open
input and output streams are automatically flushed and closed. Attempts
to further use those streams result in an IOException. The
FileConnection instance object remains open and available for use,
referring now to the file or directory by its new name.

Parameters:

newName - The new name of the file or directory. The name must
not contain any path specification; the file or directory
remains in its same directory as before this method call.

Throws:

IOException - if the connection's target does not exist, the
connection's target is not accessible, a file or directory
already exists by the newName, or
newName is an invalid filename for the platform
(e.g. contains characters invalid in a filename on the platform).

setFileConnection

Resets this FileConnection object to another file or directory. This
allows reuse of the FileConnection object for directory traversal. The
current FileConnection object must refer to a directory, and the new
file or directory must exist within this directory, or may be the
string ".." used to indicate the parent directory for the current
connection). The FileConnection instance object remains open and
available for use, referring now to the newly specified file or
directory.

Parameters:

fileName - name of the file or directory to which this
FileConnection is reset. The fileName must be one of the
values returned from the list() method, or the string
".." to indicate the parent directory of the current
connection. The fileName must not contain any additional path
specification; i.e. the file or directory must reside within
the current directory.

SecurityException - if the security of the application does not
have the security access to the specified file or directory
as requested in the Connector.open method
invocation that originally opened this FileConnection.

IOException - if the current FileConnection is opened on a file,
the connection's target is not accessible, or
fileName is an invalid filename for the platform
(e.g. contains characters invalid in a filename on the platform), or
the current connection is connected to the file system's root and
the fileName parameter is "..".

setHidden

Sets the hidden attribute of the selected file to
the value provided. The attribute is applied to the file on the actual
file system immediately upon invocation of this method if the file system
and platform support it. If the file system doesn't support a hidden
attribute, this method is ignored and isHidden() always
returns false. Since the exact definition of hidden is system-dependent,
this method only works on file systems that support a settable file
attribute. For example, on Win32 and FAT file systems, a file may be
considered hidden if it has been marked as such in the file's
attributes; therefore this method is applicable. However on UNIX
systems a file may be considered to be hidden if its name begins with a
period character ('.'). In the UNIX case, this method may be ignored and
the method to make a file hidden may be the rename() method.

Parameters:

hidden - The new state of the hidden flag of the selected file.

Throws:

IOException - if the connection's target does not exist or is not
accessible.

setReadable

Sets the file or directory readable attribute to the
indicated value. The readable attribute for the file on the actual
file system is set immediately upon invocation of this method. If the
file system doesn't support a settable read attribute, this method is
ignored and canRead() always returns true.

Parameters:

readable - The new state of the readable flag of the selected file.

Throws:

IOException - of the connection's target does not exist or is not
accessible.

setWritable

Sets the selected file or directory writable attribute to the
indicated value. The writable attribute for the file on the actual
file system is set immediately upon invocation of the method. If the
file system doesn't support a settable write attribute, this method is
ignored and canWrite() always returns true.

Parameters:

writable - The new state of the writable flag of the selected file.

Throws:

IOException - if the connection's target does not exist or is not
accessible.

truncate

Truncates the file, discarding all data from the given byte offset to
the current end of the file. If the byte offset provided is greater
than or equal to the file's current byte count, the method returns
without changing the file. Any open streams are flushed automatically
before the truncation occurs.

Parameters:

byteOffset - the offset into the file from which truncation
occurs.

Throws:

IOException - if invoked on a directory or the file does not exist
or is not accessible.